Beach-goers are cleared from the water at Bondi Beach after a shark alarm sounded on Friday. Photo: Peter Braig

While shark bites are rare and random events, and just below half of all encounters end without injury to the person or shark, there have been a higher number of fatal shark bites in the past year.

Last year five people died from shark bites, compared with two people in 2013 and 2012.

Growing populations near coastal areas and improvements to wetsuits and scuba-diving equipment mean swimmers and surfers are spending more time in the water throughout the year.

The Australian Shark Attack File recorded an average of 15 incidents per year between 2000 and 2009, an increase from 6.5 incidents in the decade from 1990. The report classifies "attacks" as any interaction between a person and a shark where the animal attempts to attack the person or their equipment.

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The data, collected by John West of the Taronga Conservation Society, shows an increase in the number of incidents in all states since 1900, in line with the country's population growth. The majority of encounters happen on the east coast and near major cities and white, bull and tiger sharks were the three species responsible for fatal shark bites.

Shark bite researcher Chris Neff said although the spate of recent shark-related deaths was "very tragic", more than 80 per cent of shark bites were not fatal. The number of fatal shark bites has fallen from an average of three a year in the 1930s to one a year between 2000 and 2009.

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The majority of shark bites in that decade occurred when the victim was surfing. Of the 79 incidents only six proved fatal and more than half ended without injury.

Dr Neff, from the University of Sydney, said the development of thicker, better insulated wetsuits also explained the rise in shark bites suffered by surfers because they could now surf for more months of the year, stay in the water longer and paddle further out.

"Back in the 30s and 40s you used the ocean two or three months of the year. Now humans run into sharks 12 months of the year, on the coldest of days because we've got better wetsuits and better kayaks that can go out further," he said.

Better scuba gear also allows divers to swim to deeper depths for longer periods of time.

"Technology has really led to an increase in human shark interactions," Dr Neff said.

Dr Neff said spearfishing was one of the most dangerous water activities associated with shark encounters because Injured fish attracted sharks. "And when you fire the gun it makes a lot of noise and that lets everyone know you're in the area."

Reliable information on the size and distribution of shark populations is hard to gather, and most data comes from animals caught in beach nets or killed as bycatch of the fishing industry. However, scientists also tag sharks to estimate their numbers.

Around the world many species of shark have declined, including the white shark, which is listed as vulnerable after years of overfishing.

Some sharks take 25 years to reach sexual maturity, which means a noticeable increase in their population would take several decades.